116 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
) 
own, thus forming a structure similar to a nucleus but containing only 
a single chromosome.” Kornhauser (15, p. 408) says concerning the 
spermatogonia of Hersilia:— “The telophase chromosomes become 
gradually fainter in outline, and a clear area in the cytoplasm begins 
to form about them. It is, I believe, the boundary between this clear 
area and the more reticular cytoplasm which forms the new nuclear 
membrane.” Thus it will be seen that it is quite usual for telophase 
chromosomes to form individual nuclei, which later fuse to form the 
whole nucleus, and with Smallwood (’05) we may accept this tendency 
as an argument for chromosomal individuality. 
(2) Theories of continuity. Among those who support a theory of 
continuity, there is not always agreement as to what structures are 
carried from one cell-generation to the next. It is generally agreed 
that the chromosomes are composed of at least two substances; the 
chromatin and the ground substance (linin, plastin). Hicker (’04) 
formulated the “Successionshypothese,” stating that the persisting 
structures of the chromosomes consisted of the “Grundsubstanz,”’ 
or achromatic part. Bonnevie (’08@) and others, on the contrary, 
regard the chromatic substance as the persistent portion and the 
achromatin as the temporary part of the chromosome. 
Vejdovsky (’07, ’11-12) has evolved a most elaborate theory touch- 
ing this problem. In his monograph of 1907, he based his conclusions 
on a study of the ovogenesis and maturation of some annelids. He 
concludes that the nucleus is derived from the chromosomes and from 
them alone. He divides the interkinetic stages into two periods; the 
one during which the nucleus is formed out of the chromosomes he 
calls “ katachromasis,”’ and the one during which the chromosomes are 
formed out of the nucleus he calls “anachromasis.” In his later 
monograph (’11-12) he analyses these processes still further and 
attempts to describe in detail the events in the two periods. His 
conclusions may be briefly stated as follows: — A chromosome is com- 
posed of two substances, one a less deeply staining substratum, on 
the surface of which is the other, the more deeply stainable chromatin. 
In the early stages of katachromasis, the chromatin differentiates into 
a spiral thread, or “chromonema,”’ which is coiled about the surface 
of the substratum. The substratum then dissolves, forming the 
nuclear sap, or “enchylema.’’ The chromonema further differentiates 
into a finely coiled chromatic portion, inside of which is a linin core. 
In this condition, he recognizes the anlage of the chromosome of the 
succeeding generation. The linin substance of the chromonema is to 
become the substratum of the future chromosome, and the finely 
